Planner’s support for storing projects in databases has been rather broken for a while. I recently fixed a bug that caused Planner to crash when you tried to save over an existing project in the database (#397132), so it was once again possible to use a database for storage. There was also a problem with newer postgresql versions (#318440), but that turned out to be a bug in postgresql that has subsequently been solved in postgresql-8.2.5.
Just last week I got a request to add support for libgda-3, because some distributions were dropping support for older libgda versions. I expected this to be more or less a configure fix, but it turns out it was quite a bit more work than that.